Ask the RD: How Are Serving Sizes Decided?

Sidney Fry, MS, RD
by Sidney Fry, MS, RD
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Ask the RD: How Are Serving Sizes Decided?

Glad you asked. Servings and portions are two distinct and separate things. A portion is the amount of food you (or the restaurant you’re dining in) choose to serve yourself at any given time or sitting. A serving is a stated or given amount, referenced and recommended by either the USDA, the FDA or the nutrition label on a box or package.

You can also think of it this way: A portion is what you pile on your plate, while a serving is a standardized measurement of food. Servings can get confusing — some are in cup measurements, some in counts (like 10 chips or crackers), some by weight, in ounces or grams.  


More important, however, these serving sizes allow food brands and manufacturers to create more uniform labels across brands, giving consumers something to compare across similar types of food. A serving is not a rigid, hard-set recommendation related to health. In fact, a serving size on a package might be larger than something a health practitioner would use to promote healthy habits — like an entire candy bar, a can of soda or a 2-ounce bag of potato chips. These numbers are important to consider, but not necessarily recommended as something we should consume in its entirety.

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Believe it or not, we actually helped decide what a given serving size would be on a label. When nutrition labeling on packages was first standardized in 1994, the USDA used results from two Nationwide Health and Nutrition Examination Surveys (NHANES). In today’s world, those surveys are extremely dated — using information that was collected between 1978–1988.


The good news is a newer, better food label has been proposed, which will include more accurate serving sizes, larger and bolder font sizes for calories, vitamin D amounts and a new requirement to include added sugars. The bad news is enforcement of these labels has been extended until early 2020.  

Labels can be tricky … and food manufacturers often lower the serving size on a label to make their numbers appear better, for example: a cereal with 3/4 cup serving size instead of 1 cup, to lower sugar by 25%. Labels do, however, serve as a good comparison tool and give great information about what exactly is in your food.

Preparing and eating food at home has a huge advantage — you get to control the portions on your own plate. Restaurant portions are notoriously larger than necessary, and research shows most of us have a tendency to clean our plates — eating more food when we are offered larger portions, regardless of appetite and satiation.


Use your plate as a general guide during meals. Fill 1/2 your plate with fruits, greens and vegetables, 1/4 with whole grains or starchy vegetables and the remaining 1/4 with high-quality proteins like seafood, lean beef or chicken, eggs, tofu or beans.

Use the palm of your hand as a serving size reference, too. Be sure to always read your labels, and stay away from foods with super lengthy ingredient lists, unfamiliar words, foods with sugar listed as the first ingredient, anything with trans fats and foods that contain artificial colors or sweeteners.

Also remember this: Often the healthiest foods are those that don’t have labels on the package at all — foods like fruits, vegetables, fresh fish, lean butcher cuts and whole grains from the bulk bin.

About the Author

Sidney Fry, MS, RD
Sidney Fry, MS, RD

Sidney is a two-time James Beard Award-winning food and nutrition writer, editor and mom based out of Birmingham, Alabama. A registered dietitian with a passion for research and being proactive about health, she loves to eat, write, run and create simple, tasty meals with whole-food-based approach. Find out more from her website, Instagram or Twitter.


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